UNIVERSITY  OF   CALIFORNIA  PUBLICATIOMS 

COLLEGE  OF  AGRICULTURE 

AGRICULTURAL  EXPERIMENT  STATION 

BERKELEY,  CALIFORNIA 


THE  DETERIORATION  OF  LUMBER 

(A  Preliminary  Study) 


BY 

MERRITT  B.   PRATT 


BULLETIN  No.  252 

Berkeley,  Cal.,  May,  1915 


UNIVERSITY  OF  CALIFORNIA  PRESS 
BERKELEY 

1915 


Benjamin  Ide  Wheeler,  President  of  the  University. 

EXPERIMENT  STATION  STAFF 
HEADS   OF   DIVISIONS 
Thomas  Forsyth  Hunt,  Director. 

Eugene  W.   Hilgard,   Agricultural  Chemistry   (Emeritus). 
Edward  J.  Wickson,  Horticulture. 

Herbert  J.  Webber,  Director  Citrus  Experiment   Station;   Plant  Breeding. 
Hubert  E.  Van  Norman,  Vice  Director;  Dairy  Management. 
William  A.   Setchell,  Botany. 
Mver  E.  Jaffa,  Nutrition. 

Robert  H.   Loughridge,  Soil  Chemistry  and  Physics    (Emeritus). 
Charles  W.  Woodworth,  Entomology. 
Ralph  E.  Smith,  Plant  Pathology. 
J.  Eliot  Coit,  Citriculture. 
John  W.  Gilmore,  Agronomy. 
Charles  F.  Shaw,  Soil  Technology. 

John  W.   Gregg,  Landscape  Gardening  and  Floriculture. 
Frederic  T.  Bioletti,  Viticulture  and  Enology. 
Warren  T.  Clarke,  Agricultural  Extension. 
John  S.  Burd,  Agricultural  Chemistry. 
Charles  B.  Lipman,   Soil  Chemistry  and  Bacteriology. 
Clarence  M.  Haring,  Veterinary  Science  and  Bacteriology. 
Ernest  B.  Babcock,  Genetics. 
Gordon  H.  True,  Animal  Husbandry. 
Arnold  V.  Stubenrauch,  Pomology. 
Fritz  W.  Woll,  Animal  Nutrition. 
James  T.  Barrett,  Plant  Pathology. 
Walter  Mulford,  Forestry. 
Walter    P.    Kelley,    Agricultural    Chemistry. 
William   G.  Hummel,  Agricultural  Education. 
Leon  M.  Davis,  Dairy  Industry. 
John  E.  Dougherty,  Poultry  Husbandry. 
Frank  Adams,   Irrigation   Practice. 
David  N.  Morgan,  Assistant  to  the  Director. 
Mrs.   D.    L.    Bunnell,   Librarian. 

Division  of  Forestry 

Walter  Mulford  Merritt  B.   Pratt 

D.  T.  Mason  Woodbridge  Metoalf 

Donald  Bruce 


CONTENTS 

PAGE 

Factors  Affecting  Deterioration  : 301 

Air-drying 301 

Yard 301 

Piling    ., 303 

Climate  and  Season  of  the  Year  304 

Dimension   of  Stock   304 

Defects  Causing  Deterioration  in  Air-diying  304 

Blue  Stain  304 

Brown  Stain 305 

Cheek  and  Warp  30? 

Pitch  : 307 

Mechanical  Defects  Due  to  Handling  309 

Kiln-drying    309 

Surfacing    312 

Data  Secured  in  the  Present  Study 322 

Air-dried  Lumber 322 

Kiln-dried  Lumber    324 

Surfaced  Lumber  32g 

Summary    327 


Digitized  by  the  Internet  Archive 

in  2012  with  funding  from 

University  of  California,  Davis  Libraries 


http://www.archive.org/details/deteriorationofl252prat 


THE  DETERIORATION  OF  LUMBER 

(A  Preliminary  Study) 
By  MERRITT  B.  PRATT 


Lumbermen  realize  that  lumber  depreciates  considerably  from  the 
time  it  leaves  the  saw  until  it  is  placed  on  board  cars,  but  have  little 
idea  of  the  amount  of  injury  and  the  possibilities  of  reducing  the  loss. 

The  present  deterioration  study  followed  the  lumber  from  the  time 
it  left  the  sawmill  until  it  was  shipped.  It  determined  as  definitely 
as  possible  the  loss  in  grade  due  to  air-seasoning,  kiln-drying,  and 
finishing  and  the  causes  leading  to  the  loss.  The  study  was  made  in 
the  yards  of  a  representative  lumber  company  in  the  northern  part 
of  the  Sierra  Nevada  Mountains  of  California,  and  the  results  ob- 
tained are  due,  in  large  measure,  to  the  co-operation  of  that  company. 
The  study  was  undertaken  at  the  suggestion  of,  and  in  co-operation 
with,  the  United  States  Forest  Service,  through  Mr.  C.  Stowell  Smith, 
Assistant  District  Forester  at  San  Francisco. 

The  data  obtained  concerns  three  species :  sugar  pine  (Pinus  lam- 
bertiana  Dougl.)  ;  western  yellow  pine  (Pinus  ponderosa  Laws.),  which 
goes  by  the  market  name  of  California  white  pine;  and  Douglas  fir 
{Pseudotsuga  taxifolia  Brit.),  often  called  spruce  in  the  market;  these 
being  the  most  valuable  timber  trees  in  the  Sierras. 

FACTORS  AFFECTING  DETERIORATION 
AIR-DRYING 

Among  the  important  factors  which  affect  the  amount  of  depreci- 
ation in  air-drying  are  the  location  of  the  yard,  the  method  of  piling 
the  lumber,  the  climate  and  season  of  the  year,  and  the  dimension  of 
the  stock. 

Yard. — The  yard  on  the  operation  studied  was  poorly  located  for 
drying  purposes.  Its  lower  part  was  located  on  a  black  loamy  soil 
which  did  not  dry  out  readily  and  supported  a  heavy  growth  of  grass 
and  weeds,  which  retarded  circulation  of  air  in  the  piles.  Good 
circulation  of  air  was  also  prevented  through  the  crowded  condition 
and  general  location  of    the  yard,  it  being  only  about  ten  acres  in 

[301] 


302 


UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION 


Fig.   1. — Yard   in  which  the  air-dried  stock   was  tallied  from  the  piles. 
Good  circulation  of  air  was  hindered  by  surrounding  mountains 


Fig.  2. — Terminus  of  flume  carrying  lumber  from  the  sawmill  four  and  a 

half  miles  distant 


extent  and  closely  hemmed  in  by  surrounding  mountains.  The  poor 
conditioning  of  the  pine  lumber  in  the  piles  in  the  lower  part  of  the 
yard  can  be  attributed  mainly  to  poor  air  circulation.  (See  fig.  1.) 
The  piles  in  the  upper  part,  located  on  well-drained  gravelly  soil  and 


Bulletin  252 


THE  DETERIORATION  OF  LUMBER 


303 


with  free  air  circulation,  dried  out  more  quickly  and  with  less  deteri- 
oration in  the  grade  of  the  lumber. 

Piling. — Satisfactory  conditioning  of  lumber  depends  in  great 
measure  on  the  way  it  is  piled.  The  following  principles  are  essential 
for  good  air-drying  of  sugar  pine:  (1)  Foundation  of  pile  should 
be  solid  and  have  good  clearance  above  ground.  (2)  Piles  should  be 
open  to  provide  for  free  circulation  of  air.  (3)  Stickers,  or  cross 
pieces,  should  be  dry  and  regularly  placed  to  hold  the  boards  straight 
while  they  are  seasoning.  (4)  Piles  should  slope  and  be  well  covered 
so  that  the  water  will  run  off  quickly.  (5)  Piles  should  not  be  placed 
too  closely  together,  since  circulation  of  air  will  be  hindered  thereby. 
(See  figs.  3  and  4.) 


Fig.  3. — Piles  of  sugar  pine  lum- 
ber. Poor  circulation  conditions  re- 
sult from  piles  being  too  close  to- 
gether, also  by  reason  of  vegetation 
around  the  piles.  View  shows  heavy 
growth  of  weeds,  which  tends  to  im- 
pede circulation  of  air  in  and  around 
the  piles. 


Fig.  4. — Better  conditions  for  dry- 
ing exist  when  piles  are  not  shut  in 
by  other  piles. 


304  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION 

These  principles  were  generally  followed  in  the  yard  studied, 
except  that  the  foundations  in  some  instances  were  too  low  and  did 
not  provide  for  enough  slope  to  the  piles  for  the  water  to  run  off 
freely.  This,  coupled  with  the  close  piling  in  some  places,  caused 
much  deterioration  in  grade  on  account  of  stain. 

The  typical  pile  was  20  feet  high  by  16  feet  wide.  The  lumber 
averaged  16  feet  long,  iy2  inches  thick,  and  12  inches  wide.  The 
courses  were  separated  by  three  2x4x6  inch  Douglas  fir  stickers 
surfaced  two  sides.  There  were  three  chimneys  6  inches  or  more  wide 
through  the  pile  and  an  average  spacing  between  the  boards  of  4 
inches.  The  cover  consisted  of  1  x  12  Douglas  fir  boards  projecting 
about  2i/2  feet  at  each  end.  The  foundation  was  18  inches  from  the 
ground  in  front  and  12  inches  in  the  back  to  give  slope  to  the  pile. 

Climate  and  Season  of  the  Year. — In  the  northern  Sierras  there  is 
very  little  humidity  in  the  air  from  June  to  October  and  a  good  breeze 
generally  prevails  during  that  period.  In  the  spring  and  fall,  on  the 
other  hand,  there  is  more  or  less  rainy  weather  and  the  circulation 
conditions  are  generally  poor.  Lumber  is  not  sawed  in  this  region 
in  the  winter.  Lumber  can  often  be  well  dried  in  from  one  to  two 
months  in  the  summer.  During  the  spring  and  fall  it  not  only  requires 
a  longer  period  to  dry  the  lumber  but  there  is  greater  depreciation 
during  seasoning. 

Dimension  of  Stock. — The  thicker  and  wider  the  lumber  the  more 
liable  it  is  to  depreciation.  The  deterioration  of  2-inch  lumber  was 
greater  than  for  thinner  stock,  especially  when  there  was  heart  on 
one  side  and  sap  on  the  other.  Stock  of  this  size  should  be  sawed  all 
sap  or  all  heart  if  possible.  It  should  also  be  cut  early  enough  in  the 
season  to  allow  the  stock  to  become  dry  before  winter. 

DEFECTS  CAUSING  DETERIORATION  IN  AIR-DRYING 

To  determine  the  loss  in  grade  during  air-drying,  each  board  was 
tallied  as  it  was  taken  down  from  the  pile  for  shipment,  the  grader 
calling  off  the  original  grade  as  made  at  the  mill  when  sawed,  the 
present  grade  after  air-drying,  the  contents  in  board  feet,  and  the 
cause  of  deterioration  in  grade,  if  any.  The  following  causes  of  de- 
terioration were  noted:  blue  stain,  brown  stain,  check  and  warp,  pitch, 
mechanical  defects  due  to  handling,  and  combinations  of  these  that 
might  change  the  original  grade  or  footage. 

Blue  Slain. — Blue  stain,  which  is  very  commonly  found  in  pine 
lumber,  is  caused,  as  a  rule,  by  a  number  of  fungi,  the  activity  of 
which  produces  discoloration  in  the  sapwood,  where  there  is  an  abund- 
ant food  supply.  The  color  is  due  in  this  case  to  the  dark  colored 
mycelium  of  the  fungus,  which  is  found  as  fine  threads  in  the  food- 


Bulletin  252]  THE  DETERIORATION  OF  LUMBER  305 

containing  wood  rays  and  the  parenchyma  cells  surrounding  the  resin 
cells.  It  is  very  likely,  however,  that  some  of  the  blue  sap  stain  is 
not  produced  by  fungi,  but  by  chemical  reactions,  the  discoloration 
often  taking  place  very  rapidly. 

Blue  stain  is  the  most  serious  cause  of  depreciation  in  lumber  with 
which  lumbermen  in  northern  California  have  to  contend.  It  develops 
to  a  large  extent  in  piles  put  up  in  the  fall  and  which  do  not  have 
time  to  dry  out  before  the  winter  rains  set  in.  It  also  develops  where 
the  drying  conditions  are  poor,  especially  where  free  circulation  of 
air  is  retarded  by  too  close  piling  or  by  a  growth  of  weeds  beneath 
the  pile.  It  is  also  brought  about  by  unfavorable  atmospheric  condi- 
tions, such  as  a  cloudy,  humid  period  extending  over  several  days  with 
little  or  no  .breeze.  Under  such  conditions  lumber  cut  in  the  spring 
or  fall  blues  very  rapidly. 

Log  stain,  which  is  a  darker  blue  and  more  deeply  embedded  than 
the  blue  stain  which  develops  in  piled  lumber,  may  be  due  to  a  chem- 
ical reaction.  It  develops  very  rapidly  in  logs  cut  and  left  in  the 
woods,  appearing  first  on  the  ends  and  gradually  extending  through 
the  sapwood  as  the  bark  becomes  loosened. 

Lumbermen  realize  the  advantages  of  open  piling  of  pine  in  com- 
batting blue  stain  and  the  necessity  of  free  circulation  of  air.  In 
many  places  the  weeds  are  killed  by  sprinkling  quicklime  on  the 
ground  where  the  piles  are  to  be  placed.  Since  humid  conditions  and 
poor  circulation  promote  blue  stain,  it  is  of  advantage  to  have  piles 
on  soil  with  low  moisture  content  and  in  positions  where  the  air  can 
circulate  freely.  When  piles  are  shut  in  by  surrounding  piles  the 
amount  of  stain  is  invariably  greater  than  when  the  piles  are  free. 

Blue  stain  does  not  injure  the  strength  of  the  wood,  since  the  walls 
of  the  wood  cells  are  not  destroyed  by  the  fungus.  It  is  the  stained 
appearance  of  the  lumber  which  seriously  decreases  its  money  value. 

It  is  a  problem  to  dispose  of  stained  lumber.  A  grade  of  stained 
clear  is  made  for  finishing  stock  and  second-class  door  cuttings  are 
secured  from  No.  2  shop,  which  admits  of  slightly  stained  sap  not 
extending  over  more  than  one-half  of  the  face  of  the  piece  on  one  side. 
This  must  be  the  only  defect,  however,  or  the  piece  will  be  graded  as 
box  lumber.  Some  companies  have  a  limited  market  for  stained  box 
shooks  for  cannery  stock.  Shippers  of  high  class  fruit,  however,  do 
not  want  a  stained  box,  since  it  detracts  from  the  appearance  of  the 
package.  A  common  method  of  getting  rid  of  stained  lower  grade 
lumber  is  to  work  it  up  into  sheathing  and  car  strips. 

Brown  Stain. — Brown  stain,  which  is  frequently  not  discernible 
in  lumber  until  it  has  been  finished,  is  a  very  serious  defect.     Its 


306  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION 

presence  is  not  due  to  fungi,  but  to  a  chemical  reaction  which  takes 
place  in  green  sap  lumber  upon  exposure  to  the  air.  When  the 
freshly  cut  surfaces  are  exposed  to  the  air,  under  favorable  conditions 
of  temperature  and  moisture,  a  chemical  reaction  results  which  pro- 
duces a  colored  substance  on  the  wood.  "Favorable  conditions  for 
sap-staining  are  found  during  warm  weather  and  optimum  conditions 
during  extremely  hot,  humid  summer  weather,  when  lumber  becomes 
discolored  within  a  few  hours.  The  examination  of  microscopic  sec- 
tions of  this  sap-stained  lumber  reveals  the  fact  that  the  colored 
substance,  produced  by  the  chemical  reaction,  is  most  conspicuously 
developed  in  the  wood  rays  and  wood  parenchyma  cells,  living  tissues 
which  are  largely  concerned  in  the  storage  and  conduction  of  food  in 
the  wood."1 

Professor  John  S.  Burd,  Agricultural  Chemist,  University  of  Cali- 
fornia, to  whom  samples  of  brown-stained  sugar  pine  lumber  were 
submitted,  comments  as  follows : 

"I  submitted  the  samples  to  Professor  R.  E.  Smith  of  the  Division 
of  Plant  Pathology,  who  reports  that  he  is  unable  to  discover  any 
organism  in  connection  with  the  brown  stain  produced.  This  confirms 
my  previous  opinion,  namely,  that  brown  stain  is  probably  due  to 
oxidation  of  certain  constituents  of  the  wood,  the  exact  character 
of  which  is  unknown.  Mr.  Hibbard  of  this  laboratory  has  treated 
samples  of  wTood  affected  by  the  brown  stain  with  a  considerable 
number  of  oxidizing  and  reducing  agents  and  has  found  it  impossible 
to  destroy  the  color  so  produced.  I  am  therefore  disposed  to  believe 
that  after  the  stain  has  once  occurred  it  will  not  be  practicable  to 
destroy  same  except  by  a  process  which  would  result  in  the  destruction 
of  the  tissues  of  the  wood.  This  means  that  in  any  attempt  to  miti- 
gate the  effects  of  brown  stain  it  will  be  necessary  to  proceed  along 
the  lines  of  prevention  rather  than  cure.  In  order  to  follow  up  such 
a  method  it  would  be  necessary  to  make  comparative  experiments  on 
timber  under  field  conditions.  Such  experiments  would  require  that 
the  wood,  seasoned  by  any  method,  should  be  checked  by  comparisons 
Avith  tests  of  the  same  timber  seasoned  by  the  usual  processes." 

Both  blue  and  brown  stains  are  closely  related  to  the  food  sub- 
stances contained  in  the  wood.  Both  of  these  agencies  are  dependent 
upon  certain  quantities  of  oxygen  from  the  air.  heat,  and  moisture. 
The  conditions  causing  the  worst  sap  staining,  bcth  blue  and  brown, 
are  found  in  green  sap  lumber  during  hot,  humid  weather ;  whereas 
conditions  tending  to  prevent  staining  are  found  in  cool,  dry  weather 
and  in  logs  immersed  in  water. 


Bailey,  Botanical  Gazette,  Vol.  50,  pp.  142-147.     August,  1910. 


Bulletin  252]  THE  DETERIORATION  OF  LUMBER  307 

Brown  stain  is  not  found  in  yellow  pine.  The  presence  of  the 
sugary  sap  in  sugar  pine  probably  has  something  to  do  with  the 
oxidizing  process,  resulting  in  brown  stain,  which  is  so  common  in 
lumber  of  that  species.  Brown  stain  is  especially  bad  in  lumber  cut 
in  early  spring,  when  the  tree  is  sappy.  It  is  generally  found  as  a 
distinct  band  between  the  heart  and  sap  wood.  Very  frequently 
boards  which  have  been  subjected  to  especially  unfavorable  drying 
conditions  have  both  blue  and  brown  stains. 

Sugar  pine  when  put  in  the  kiln  is  very  subject  to  kiln-burn,  which 
cannot  be  detected  in  surfaced  lumber  from  the  brown  stain  found  in 
air-dried  lumber.  In  fact,  it  is  probable  that  it  is  brown  stain  caused 
through  defective  circulation  conditions  in  the  kiln  the  same  as  in 
the  pile.     (See  fig.  5.) 

Check  and  Warp. — No  checking  can  occur  until  the  surface  of  the 
wood  has  lost  all  its  free  water,  that  is,  water  in  liquid  form  filling 
the  pores.  When  the  circulation  of  air  is  defective  the  transmission 
of  water  from  the  interior  of  the  board  to  the  surface  does  not  go  on 
uniformly,  uneven  drying  takes  place  and  case-hardening,  followed 
by  checking,  results. 

End  checks  are  common  on  account  of  shrinkage  caused  by  the 
ends  of  boards  drying  out  more  rapidly  than  the  face.  If  a  freshly 
cut  board  is  exposed  to  the  sun,  the  top  surface  dries  out  more  rapidly 
than  the  lower  surface,  and  on  account  of  the  uneven  drying  warping 
takes  place.  Uneven  seasoning,  therefore,  results  in  checking  and 
warping.  Much  check  and  warp  can  be  avoided  by  putting  sun  covers 
on  the  piles  during  intervals  of  piling,  especially  on  high  grade  stock, 
which  does  not  accumulate  very  rapidly. 

The  harder  the  grain  the  greater  is  the  liability  to  check  and 
warp.  This  was  evidenced  in  several  cribs  of  kiln-dried  cross-grained 
Douglas  fir  stock,  a  large  proportion  of  which  was  checked  and  warped. 
Sugar  pine  does  not  suffer  in  grade  from  these  causes  nearly  so  much 
as  yellow  pine  on  account  of  its  softer  texture.  Yellow  pine  and 
Douglas  fir  check  and  warp  very  badly  when  piled  in  the  yard,  conse- 
quently the  upper  grades  are  kiln-dried  by  the  majority  of  lumber 
companies  in  this  region. 

Pitch. — -Oftentimes  pitch  which  is  not  discernible  in  the  board  on 
the  grading  tables  at  the  mill  appears  in  seasoning,  both  in  the  air- 
dried  pile  and  in  the  kiln.  It  is  a  very  common  cause  of  misgrade 
at  the  sawmill.  Pitch  may  occur  in  small  pockets  or  in  streaks,  often 
resulting  in  the  lowering  of  the  grade.  An  Australian  grade  is  made 
which  admits  of  considerable  pitch,  but  it  is  a  serious  defect  in 
finishing  stock  used  in  this  country. 


308  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION 


Fig.  5. — Brown  stain  in  sugar  pine  lumber 


Fig.  6. — Kiln-burn  in  sugar  pine  lumber 


Bulletin  252]  THE  DETERIORATION  OF  LUMBER  309 

Boards  taken  from  the  butt  ends  of  trees  which  have  been  fire 
scarred  are  very  pitchy  as  a  rule.  Pitch  develops  wherever  the  tree 
has  been  injured  in  any  way.  Pitch  seams  are  found  along  lines  of 
cleavage  caused  by  wood  shake  or  frost  crack.  On  kiln-dried  boards 
pitch  globules  are  often  found,  the  pitch  having  been  forced  out  of 
the  boards  by  the  heat  and  coagulated  on  the  outside. 

Mechanical  Defects  Due  to  Handling. — On  the  operation  studied 
injury  from  handling  came  about  in  three  ways: 

Handling  of  logs  in  woods  in  mill. — Sugar  pine  boards  cut  from 
the  outside  of  a  thin-barked  log  are  often  lowered  in  grade  through 
too  deep  dogging  in  the  woods.  The  turning  of  the  logs  in  the  mill 
with  the  steam  niggers  sometimes  mars  or  breaks  the  board  so  that 
the  grade  is  reduced. 

Handling  of  lumber  in  flume. — The  lumber  was  transported  in  a 
30-inch  V-shaped  flume  four  and  a  half  miles  in  length.  (See  fig.  2.) 
The  upper  grades  are  often  broken  or  split  by  the  impact  of  heavy 
timbers.  Jams  sometimes  result,  the  boards  being  thrown  out  on  the 
rocks  below.  Heavy  sugar  pine  boards,  known  as  "sinkers,"  become 
waterlogged  and  sink,  and  the  handling  they  receive  from  the  iron 
hooks  of  the  men  on  the  flume  often  materially  reduces  the  grade. 
The  wider  the  boards  the  greater  is  the  danger  of  injury  in  the  flume. 
In  fact,  the  damage  is  so  great  that  wide  boards  are  not  cut  when 
the  water  is  low. 

Handling  in  yards.— A  very  common  source  of  injury  comes  about 
in  the  dumping  of  the  lumber  from  the  flume  to  the  skid  through 
breakage  or  splitting  of  the  ends  of  the  boards.  The  lumber  is  handled 
several  times  after  it  leaves  the  skids  and  before  it  is  placed  on  board 
cars.  Breakage  begun  in  the  flume  is  apt  to  become  intensified  every 
time  the  lumber  is  handled.  The  piling  jacks  used  in  getting  boards 
to  the  tops  of  piles  dig  holes  into  boards  unless  carefully  handled. 
The  loss  from  handling  in  the  yard,  however,  is  a  small  item  compared 
with  the  loss  in  fluming.     (See  fig.  7.) 

KILN-DRYING 

The  artificial  seasoning  of  the  upper  grades  of  lumber  in  dry-kilns 
is  being  resorted  to  more  and  more  by  lumbermen,  now  that  methods 
have  been  perfected  whereby  nearly  all  kinds  of  lumber  can  be  seasoned 
with  a  small  percentage  of  loss. 

There  are  three  conditions  which  must  be  carefully  looked  after 
if  lumber  is  to  be  kiln-dried  successfully.  These  are  heat,  air  circu- 
lation, and  humidity.  If  each  of  these  factors  can  be  properly  con- 
trolled the  lumber  can  be  successfully  dried.  To  avoid  split,  warp, 
and  check  it  is  essential  that  a  definite  relation  be  maintained  between 


310  UNIVERSITY  OF  CALIFORNIA — EXPERIMENT  STATION 

the  evaporation  from  the  surface  and  the  transmission  of  moisture 
within  the  board.  This  condition  can  be  obtained  by  observing  the 
following  principles : 

(1)  The  temperature  of  the  lumber  must  be  maintained  uniformly 
throughout  the  entire  pile. 

(2)  A  large  and  continuous  circulation  of  air  must  be  maintained. 

(3)  Control  of  the  drying  process  at  any  given  temperature  must 
be  secured  by  controlling  the  relative  humidity,  not  by  decreasing  the 
air  circulation.  This  may  be  accomplished  either  by  suitable  venti- 
lation or  by  having  steam  jets  in  the  kiln.2 

The  kiln  used  in  the  operation  studied  is  an  old  type,  operated 
by  the  steam  heat  blower  system,  live  steam  being  carried  to  the  steam 
coils  from  the  boiler.  The  heated  air  is  forced  through  ventilators 
in  the  front  of  the  kiln,  up  through  the  lumber  to  the  top  and  down 
the  side  walls  to  the  air  drum,  which  carries  it  again  to  the  steam 
coils.  A  continuous  circulation  of  air  is  kept  up  by  a  fan  situated 
in  front  of  the  steam  coils.  Lumber  is  gradually  moved  to  the  dis- 
charging end  of  the  kiln,  the  moisture  being  taken  up  by  the  heated 
air  until  the  lumber  reaches  the  degree  of  dryness  desired. 

Temperature,  humidity,  and  air  circulation  Avere  exceptionally  well 
regulated  in  the  kiln  studied,  but  the  loss,  although  less  than  in  air- 
drying,  is  a  considerable  item.  The  loss  in  grade  was  chiefly  due  to 
check,  split,  and  warp  in  yellow  pine  and  Douglas  fir  and  kiln-burn 
and  check  in  sugar  pine. 

The  checking  and  splitting  took  place  generally  in  hard,  cross- 
grained  pieces.  It  also  was  found  in  cribs  of  lumber  where  the  proper 
relations  had  not  been  maintained  between  the  evaporation  from  the 
surface  and  the  transmission  of  moisture  within  the  board. 

Kiln-burn  in  sugar  pine  usually  causes  such  a  large  amount  of 
deterioration  that  many  operators  do  not  attempt  to  kiln-dry  it,  except 
when  it  must  otherwise  be  left  to  dry  in  the  yards  over  winter.  In 
this  case  the  upper  grades  are  put  in  the  kiln  with  the  idea  that  the 
lumber  could  not  possibly  be  spoiled  to  a  greater  degree  than  if  left 
green  in  the  yard. 

The  system  of  kiln-drying  sugar  pine  has  usually  been  that  of 
keeping  a  low,  steady  temperature  during  the  entire  drying  period. 
The  experiment  was  made  in  the  kiln  studied  of  subjecting  sugar  pine 
to  the  same  heat  as  yellow  pine,  starting  with  130°  and  gradually 
raising  it  to  180°  before  the  lumber  was  removed  from  the  kiln.  The 
kiln-burn  was  much  less  with  this  method  than  under  the  low  heat 
system.  Much  investigation,  however,  is  needed  before  this  matter 
can  be  definitely  settled.     (See  fig.  6.) 

2  Tiemann,  Principles  of  Drying  Lumber  at  Atmospheric  Pressure,  Bulletin 
104,  Forest  Service,  U.  S.  Dept.  of  Agr.,  p.  6. 


Bulletin  252] 


THE  DETERIORATION  OF  LUMBER 


311 


Fig.  7. — Lumber  on  skids  as  dumped  from  the  flume 


SMWHB|^HnHKs^;«^MB|«|HHHHM^Hapr  -   <rrj§t-ir"< 

IwiiflHSHHlMBI 

B|jt  1  IjiW!1.'1  -W.J""1  ^^^^^^mlimmmmmmjjfMJ^          Pjt, 

iPgp'^lr?-  •       '  '  Hi- 

Fig.   8. — Crib  of  kiln-dried  yellow  pine  ready  to  be  regraded.     Lateral 

chimneys  shown 


312  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION 

SURFACING 

The  grade  of  lumber  as  taken  down  from  the  pile  or  from  the  kiln 
does  not  always  hold  after  it  has  been  surfaced.  Planing  may  improve 
the  grade  by  removing  the  defects  which  kept  the  grade  down  in  the 
rough,  but  it  generally  brings  to  light  defects  such  as  brown  stain 
or  check  that  were  not  before  discernible,  therebj^  causing  the  grade 
to  fall. 

In  order  to  secure  this  factor  of  reduction,  a  quantity  of  lumber 
that  had  already  been  tallied  from  the  kiln  or  from  the  yard  was 
tallied  through  the  planer,  the  complete  history  being  obtained  from 
the  time  the  lumber  left  the  mill  until  it  was  put  on  board  cars. 

DATA  SECUEED  IN  THE  PRESENT  STUDY 
The  following  are  the  average  prices  received  for  the  different 
grades  of  lumber  in  this  vicinity  at  the  time  the  study  was  made  and 
upon  which  the  monetary  loss  as  given  is  based: 

Pine 

Selling 
price  per 
Grade  1000  bd.  ft. 

No.  1  and  No.  2  clear  sugar  pine  $54.00 

No.  1  and  No.  2  clear  yellow  pine 40.00 

No.  3  clear  sugar  pine  42.00 

No.  3  clear  yellow  pine    35.00 

No.  1  shop  sugar  pine  29.00 

No.  1  shop  yellow  pine  26.00 

No.  2  shop  sugar  pine  20.00 

No.  2  shop  yellow  pine  17.50 

Australian  34.50 

Stain  clear  30.00 

Box  15.00 

Douglas  Fir 

Selling 
price  per 
Grade  1000  bd.  ft. 

Clear    $27.50 

Select  22.50 

No.  1  and  No.  2  dimension  16.50 

No.  3  dimension  12.00 

AIR-DRIED  LUMBER 

Sugar  pine  lumber  was  tallied  from  piles  which  had  been  put  up 
in  the  fall,  spring,  and  summer,  since  it  is  evident  that  drying  condi- 
tions vary  considerably  with  the  season  irrespective  of  the  way  the 
pile  is  put  up.  The  percentage  of  loss  varied  greatly,  the  greatest 
depreciation  in  grade  being  found  in  the  fall-piled  lumber  and  the 


Bulletin  252] 


THE  DETERIORATION  OF  LUMBER 


313 


least  in  the  summer-piled  stock.  Blue  stain  was  especially  bad  in  fall 
piles.  The  following  tables  show  the  amount  of  depreciation  under 
various  conditions. 

F  all-Piled  Sugar  Pine 
Total  amount  tallied,  41,812  bd.  ft. 


Original 
grade 

Thickness 

of  lumber, 

inches 

Proportion 

of  lumber 

deteriorating 

in  grade, 

per  cent 

Chief  cause  of 

deterioration  and 

proportion  of  all 

lumber  in  pile 

affected  by  it 

Loss  per 
1000  bd.  ft 
from  all 
causes, 
dollars 

1  and  2  clear* 

6/4 

75.5 

Blue 

stain,  52% 

17.90 

3  clear 

6/4 

71.2 

Blue 

stain  and  check, 

54% 

11.27 

1  shop 

5/4 

70.6 

Blue 

stain  and  check, 

36% 

8.87 

1  shop 

4/4 

68.0 

Blue  and  brown  stains 

62% 

9.96 

::  Field  data  on  one  pile  1  and  2  clear  taken  by  Swift  Berry,  Forest  Examiner, 
U.  S.  Forest  Service. 

Spring-Piled  Sugar  Pine 

Total  amount  tallied,  51,147  bd.  ft. 

Chief  cause  of 

deterioration  and 

proportion  of  all 

lumber  in  pile 

affected  by  it 

Blue  stain  and  check,  21% 
Blue  stain  and  check,  43% 
Blue  stain  and  check,  15% 
Blue  stain  and  check,  24% 

Summer-Piled  Sugar  Pine 
Total  amount  tallied,  225,156  bd.  ft.* 


Original 
grade 

Thickness 

of  lumber, 

inches 

Proportion 

of  lumber 

deteriorating 

in  grade, 

per  cent 

1  shop 

6/4 

41 

1  shop 

8/4 

56 

2  shop 

6/4 

21 

2  shop 

8/4 

36 

Loss  per 

1000  bd.  ft. 

from  all 

causes, 

dollars 

4.23 
6.35 
1.11 

1.82 


Original 
grade 

1  and  2  clear 
3  clear 
Australian 
1  shop 

1  and  2  clear 
3  clear 
Australian 
1  shop 


Proportion 
of  lumber 
Thickness  deteriorating 
of  lumber,      in  grade, 


1  and  2 
3  clear 
1  shop 


clear 


inches 


4/4 


5/4 


6/4 


per  cent 


11.6 


11 


13.2 


Chief  cause  of 

deterioration  and 

proportion  of  all 

lumber  in  pile 

affected  by  it 


Blue  stain  and  handling,  8.1 


Blue  stain  and  handling, 

Check,  2.8% 
Handling,  4.2% 
Blue  stain,  2.6% 
Brown  stain,  2% 


1  and  2  clear      -> 

3  clear  Check,  11.7% 

Australian  I  8/4  29.7  Blue  stain,  8.4% 

1  shop  Handling,  4% 

2  shop 

*  This  lumber  was  tallied  by  S.  B.  Show,  Forest  Examiner,  and 

Forest  Ranger,  both  of  the  U.  S.  Forest  Service. 


314  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION 

The  lumber  which  was  found  to  have  held  its  grade  in  the  No.  2 
shop  piles  in  the  spring-piled  sugar  pine,  amounting  to  19,838  board 
feet,  was  then  surfaced  on  two  sides  for  shipment  and  again  graded 
after  surfacing.  Some  of  the  defects  surfaced  out,  while  others,  par- 
ticularly brown  stain,  appeared.  There  was  a  gain  of  47  cents  per 
thousand  board  feet  in  the  lot  from  one  pile  of  No.  2  shop  and  a  loss 
of  31  cents  per  thousand  board  feet  in  the  other  pile  through  surfacing. 

Mr.  Show  also  tallied  5310  board  feet  of  No.  3  clear  sugar  pine, 
which  was  surfaced  two  sides  directly  after  it  had  been  taken  down 
from  a  pile  of  summer-dried  stock.  It  was  found  that  there  was  a 
loss  of  $1.44  per  thousand  board  feet  due  to  blue  and  brown  stains 
which  did  not  show  up  in  the  rough. 

KILN-DRIED  LUMBER 

Sugar  Pine. — It  has  not  been  the  practice  of  the  lumber  company 
in  whose  yards  this  study  was  made  to  kiln-dry  sugar  pine  because  of 
the  loss  to  which  it  was  thought  it  would  be  subject  from  kiln-burn. 
An  experimental  run  of  14,000  board  feet  of  No.  1  and  No.  2  shop 
was  made,  however,  to  compare  the  loss  in  grade  with  summer  air- 
dried  stock.  The  following  comparatively  small  loss  was  the  surprising 
result : 


Total  amount  tallied,  14,000  bd.  ft. 

Original 
grade 
1    shop 

Proportion 
of  lumber 
Thickness      showing 
of  lumber,  deterioration 
inches          per  cent 
6/4                  8 

Chief  cause  of 
deterioration 

Check  and  kiln-burn 

Loss  per 

1000  bd.  ft. 

from  all 

causes, 

dollars 

1.82 

1  shop 

8/4 

12 

Check  and  kiln-burn 

1.90 

2  shop 

6/4 

2 

Check  and  kiln-burn 

.11 

2  shop 

8/4 

5 

Check  and  kiln-burn 

.27 

The  lumber  which  held  its  grade,  amounting  to  9028  board  feet, 
was  then  surfaced  and  again  graded.  Additional  check  and  kiln -burn 
appeared,  causing  a  further  depreciation  of  26  cents  per  thousand 
board  feet  for  No.  1  shop  and  5  cents  per  thousand  board  feet  for 
No.  2  shop. 

Western  Yelloiv  Pine. — The  lumber  was  piled  wide  apart  so  that 
every  board  would  be  exposed  to  the  warm  air  and  evaporation  of 
moisture  would  take  place  readily.  There  was  an  average  of  twenty- 
eight  courses  of  iy2-inch  lumber  to  the  car,  with  three  lateral  4-inch 
chimneys  made  by  placing  2x4  inch  stickers  at  the  bottom  of  the 


Bulletin  252]  THE  DETERIORATION  OF  LUMBER  315 

twelfth,   eighteenth,   and  twenty-fourth  courses  from  the  top.     The 
average  length  of  drying  was  ten  days.     (See  fig.  8.) 

Total  amount  tallied,  80,000  bd.  ft. 


Original 
grade 

Thickness 

of  lumber, 

inches 

Proportion 

of  lumber 

showing 

deterioration 

per  cent 

Chief  cause  of 
deterioration 

Loss  per 

1000  bd.  ft. 

from  all 

causes, 

dollars 

1  and  2  clear 

4/4 

5 

Check 

.70 

1  and  2  clear 

5/4 

14 

Check 

1.25 

1  and  2  clear 

6/4 

6 

Check 

.71 

1  and  2  clear 

8/4 

23 

Check 

3.41 

3  clear 

6/4 

6 

Check 

.64 

3  clear 

8/4 

23 

Check 

3.46 

Australian 

8/4 

23 

Check 

2.42 

1  shop 

4/4 

5 

Check 

.85 

1  shop 

6/4 

6 

Check 

.64 

1  shop 

8/4 

23 

Check 

2.31 

2  shop 

8/4 

23 

Check 

.65 

A  further  depreciation  was  found  to  take  place  in  yellow  pine 
lumber  which  was  surfaced  after  being  taken  directly  from  the  kiln. 
as  shown  in  the  following  table : 

Total  amount  tallied,  12.709  bd.  ft. 

Proportion  Loss  per 

of  lumber  Chief  1000  bd.  ft. 

Thickness       showing  cause  of  from  all 

Original           of  lumber,  deterioration,  deterio-  causes, 

grade                  inches          per  cent  ration  dollars 

3  clear      8/4      6      Check      .72 

1  shop       8/4      4      Check      .70 

2  shop       6/4      2      Check      .11 


Douglas  Fir. — The  lumber  was  piled  very  closely  to  keep  it  from 
drying  out  too  quickly.  There  was  an  average  of  thirty-four  courses 
of  inch  lumber  to  the  car,  with  two  lateral  4-inch  chimneys  made  by 
placing  2x4  inch  stickers  at  the  bottom  of  the  eighteenth  and  twenty- 
eighth  courses  from  the  top.  Douglas  fir  lumber  in  this  vicinity  is 
of  very  hard  texture  and  warps  and  checks  badly  if  not  carefully 
treated  in  the  kiln.  Even  then  cross-grained  stock  warps  and  splits 
because  of  its  extreme  hardness.  The  few  pieces  of  2-inch  lumber  put 
in  with  the  inch  stock  showed  a  large  proportion  of  check.  The  average 
length  of  drying  was  five  days. 


316  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION 

Total  amount  tallied,  53,000  bd.  ft. 


Original 
grade 

Clear 

Thickness 

of  lumber, 

inches 

4/4 

Proportion 

of  lumber 

showing 

deterioration. 

per  cent 

9 

Chief  cause  of 
deterioration 

Check  and  warp 

Loss  per 
1000  bd.  ft 
from  all 
causes, 
dollars 

.73 

Clear 

8/4 

16 

Check  and  warp 

2.91 

Clear 

4/4 

9 

Check  and  warp 

.32 

SURFACED  LUMBER 

111  addition  to  the  surfaced  lumber  amounting  to  19,838  board  feet 
of  spring-piled  air-dried  sugar  pine,  5310  board  feet  of  summer-piled 
air-dried  sugar  pine,  9028  board  feet  of  kiln-dried  sugar  pine,  and 
12,709  board  feet  of  kiln-dried  yellow  pine,  which  was  again  graded 
directly  after  it  had  been  taken  from  the  pile  and  kiln  and  the  results 
of  which  have  already  "been  stated,  the  following  data  were  taken 
regarding  change  in  grade  due  to  surfacing  of  lumber  which  had  been 
stored  in  sheds. 

Sugar  Pine,  Surfaced  Two  Sides. — The  lumber  in  the  following- 
table  had  been  graded  down  from  the  piles  the  year  before  and  stored 
in  the  sheds  until  needed.  The  brown  stain  shown  in  surfacing  either 
was  not  detected  by  the  grader  in  the  rough  or  developed  in  storage, 
since  this  proportion  of  deterioration  was  not  found  in  lumber  taken 
directly  from  the  piles  to  the  planer. 

Total  amount  tallied,  38,000  bd.  ft. 


Proportion 

Chief  cause  of 

Loss  per 

of  lumber 

deterioration  and 

1000  bd.  ft. 

Thickness  deteriorating 

proportion  of  all 

from  all 

Original 

of  lumber,       in  grade, 

surface  lumber 

causes, 

grade 

inches          per  cent 

affected  by  it 

dollars 

1  shop 

5/4               54 

Brown  stain,  32% 

7.43 

1  shop 

8/4               45 

Brown  stain,  24% 

5.45 

2  shop 

6/4              31 

Brown  stain,  21% 

1.54 

Considerable  trouble  is  experienced  in  shipping  sugar  pine  because 
of  brown  stain.  Cases  have  been  known  where  there  was  apparently 
no  brown  stain  in  the  lumber  at  the  time  it  was  shipped,  but  which 
was  found  by  the  consignee  when  the  car  reached  him.  One  company 
lost  a  hundred  dollars  on  a  car  of  high  grade  stock  through  brown 
stain,  which  was  not  apparent  at  the  time  of  shipping.  The  proba- 
bilities are  that  the  lumber  was  not  thoroughly  dry  when  it  was 
shipped.  The  many  complaints  along  this  line  are  leading  lumbermen 
dealing  in  sugar  pine  to  use  the  utmost  care  in  its  seasoning. 


Bulletin  252]  the  deterioration  OF  LUMBER  317 

Western  Yellow  Pine,  Surfaced  Tire)  Sides. —  As  a  basis  of  compar- 
ison with  the  loss  sustained  by  sugar  pine  taken  from  the  sheds,  kiln- 
dried  yellow  pine  which  had  also  been  stored  was  followed  through  the 
planer  and  tallied  when  loaded  on  board  cars.  The  absence  of  brown 
stain  made  the  loss  per  thousand  board  feet  much  lower  than  for  sugar 
pine,  but  it  was  greater  than  for  lumber  surfaced  after  being'  taken 
directly  from  the  kiln.  A  greater  amount  of  check  was  apparent, 
which  may  have  been  due  to  storage  conditions. 

Total  -mount  tallied,  29,103  bd.  ft. 

Loss  per 
Proportion  1000  bd.  ft. 

Thickness      of  lumber  from  all 

Original  of  lumber,  deteriorating  Chief  cause  of      causes, 

grade  inches  per  cent       deterioration         dollars 

1   and  2  clear  4/4  5  Check  1.63 

1  and  2   clear  6/4  10  ('heck  3.22 

1   and  2   clear  8/4  3  Check  1.97 


SUMMARY 

The  data  gathered  in  this  preliminary  study  are  not  sufficient  in 
amount,  range  of  conditions,  or  length  of  time  to  warrant  a  statement 
of  final  conclusions  either  as  regards  the  amount  of  the  loss  or  the 
best  means  of  reducing  that  loss.  The  object  of  this  report  is  to  call 
attention  to  the  fact  that  this  is  a  problem  worthy  of  careful  study 
and  to  make  available  at  once  such  data  as  are  now  at  hand.  The 
United  States  Forest  Service  is  conducting  much  more  extensive 
investigations  along  the  same  line  over  a  wide  range  of  conditions. 

The  present  figures  show  that  the  loss  due  to  depreciation  in  the 
grade  of  the  lumber  from  the  time  it  leaves  the  sawr  until  it  is  shipped 
is  far  greater  than  was  generally  imagined.  This  is  especially  true 
for  sugar  pine,  which  is  considered  the  most  valuable  species  in  the 
Sierras  and  for  which  the  highest  stumpage  rate  is  asked  by  the 
United  States  Forest  Service.  Sugar  pine  lumber  appears  to  be  ex- 
tremely susceptible  to  depreciation,  particularly  to  blue  stain  and 
brown  stain.  On  account  of  the  rate  at  which  it  deteriorates  in  this 
locality,  the  company  in  whose  yards  data  concerning  it  were  taken 
contends  that  it  is  making  more  profit  on  its  western  yellow  pine 
(known  to  the  trade  as  California  white  pine),  the  upper  grades  of 
which  can  be  kiln-dried  without  an  undue  amount  of  loss.  If  sugar 
pine  could  be  kiln-dried  successfully,  and  it  is  believed  that  this  will 
be  done  in  a  short  time,  the  present  large  loss  through  air-seasoning 
would  he  greatly  decreased. 


318  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION 

The  following  conclusions  regarding  the  deterioration  of  the  upper 
grades  of  sugar  pine,  western  yellow  pine,  and  Douglas  fir  from  the 
time  the  lumber  leaves  the  sawmill  until  it  is  ready  for  shipment  are 
indicated  by  the  limited  amount  of  data  thus  far  available. 


SUGAR  PINE 

1.  The  upper  grades  of  sugar  pine  deteriorated  much  more  in 
seasoning  than  did  western  yellow  pine  or  Douglas  fir.  Of  the  sugar 
pine  lumber  of  the  upper  grades,  the  percentage  which  deteriorated 
in  grade  during  air-seasoning  was  approximately  71  per  cent,  38  per 
cent,  and  16  per  cent  for  the  fall,  spring,  and  summer  drying,  respec- 
tively. When  surfaced  there  was  a  further  deterioration  due  to  brown 
stain ;  this  was  greater  in  the  lumber  taken  from  the  storage  sheds 
than  in  that  taken  direct  from  the  piles. 

2.  The  average  loss  for  all  lumber  tallied  in  unfinished  upper 
grades  of  sugar  pine  through  fall  seasoning  was  approximately  $12 
per  thousand  board  feet  as  compared  with  an  average  loss  of  $2.58 
per  thousand  board  feet  through  summer  seasoning.3  The  average 
loss  through  spring  seasoning  cannot  be  given  in  comparable  terms, 
inasmuch  as  no  spring  seasoned  lumber  above  No.  1  shop  was  tallied. 
From  the  loss  in  No.  1  shop,  however,  it  is  estimated  that  the  average 
loss  in  spring  seasoning  for  all  the  upper  grades  was  about  $5  per 
thousand  board  feet. 

3.  One  experiment  in  kiln-drying  sugar  pine  at  the  same  temper- 
ature as  western  yellow  pine  and  Douglas  fir  indicated  that  the  deteri- 
oration in  the  upper  grades  of  sugar  pine  lumber  would  be  much  less 
if  kiln-dried  than  when  air-dried  in  the  spring  or  fall.  Ninety-three 
per  cent  of  the  small  amount  of  No.  1  and  No.  2  shop  lumber  which 
was  run  through  the  kiln  retained  its  original  grade,  and  there  was 
an  average  loss  of  only  $1  per  thousand  board  feet  for  all  the  lumber 
in  this  lot.  The  depreciation  in  surfacing  caused  an  additional  loss 
of  26  cents  per  thousand  board  feet  for  No.  1  shop  and  5  cents  per 
thousand  for  No.  2  shop.  This  total  loss  is  about  the  same  as  that 
of  air-dried  summer-piled  lumber  of  these  grades.  Until  the  matter 
of  kiln-drying  sugar  pine  has  been  worked  out  more  satisfactorily, 
however,  it  seems  preferable  to  air-dry  the  summer-cut  stock. 

4.  Blue  stain  and  brown  stain,  the  greatest  sources  of  depreciation 
in  sugar  pine  lumber,  are  largely  the  result  of  poor  drying  conditions. 


3  The  average  is  computed  for  all  lumber,  including  that  which  did  not 
deteriorate  at  all.  The  relative  amounts  and  thickness  of  each  grade  were  not 
considered  in  making  the  averages,  which  are  only  approximate.  For  losses  by 
grades  see  tables  given  previously. 


Bulletin  252]  THE  DETERIORATION  OF  LUMBER  319 

i.e.,  imperfect  circulation  of  air,  poorly  drained  soil,  failure  of  the 
pile  to  shed  rainwater,  or  damp,  rainy  weather.  It  is  necessary  that 
the  air  should  circulate  above,  below,  and  around  each  board.  Less 
stain  developed  in  piles  in  the  open  than  in  those  shut  in  and  less  in 
piles  which  were  located  on  well  drained  areas  than  when  on  soils 
retentive  of  moisture.  Stain  developed  to  a  great  extent  in  piles  put 
up  in  the  fall  when  humid  atmospheric  conditions  prevailed.  Some 
piles  put  up  in  the  spring  showed  stain  more  than  others,  depending 
on  their  location.  In  summer,  when  dry,  breezy  conditions  prevailed, 
the  lumber  did  not  depreciate  any  more  from  stain  than  from  other 
agencies,  such  as  check  and  handling. 

5.  Although  the  heavy  loss  of  grade  in  air-seasoned  sugar  pine  is 
due  in  part  to  poor  yards  and  handling,  yet  under  any  conditions  of 
seasoning  a  large  loss  is  liable  to  occur,  due  to  the  sensitiveness  of 
the  wood  to  blue  stain  and  brown  stain.  This  characteristic  of  the 
lumber  should  be  considered  in  fixing  stumpage  rates ;  the  value  should 
be  fixed  in  accordance  with  the  ultimate  grade  and  value  of  the  species 
rather  than  its  grade  and  value  at  the  saw.  The  present  data  lead 
to  the  conclusion  that  the  proper  relationship  does  not  now  exist  in 
the  vicinity  studied  between  the  stumpage  price  paid  for  sugar  pine 
and  for  western  yellow  pine. 


WESTERN  YELLOW  PINE    (CALIFORNIA   WHITE  PINE) 

Experience  has  proved  that  air-dried  western  yellow  pine  lumber 
checks  so  badly  in  this  vicinity  that  it  pays  to  kiln-dry  all  of  the 
upper  grades.  Approximately  80  per  cent  of  the  western  yellow  pine 
tallied  in  this  study  retained  the  original  grade  as  made  at  the  mill 
after  the  lumber  had  been  kiln-dried  and  surfaced.  The  average  loss 
through  deterioration  during  kiln-drying  of  the  upper  grades  was 
approximately  $1.55  per  thousand  board  feet.  When  the  lumber  was 
surfaced  on  two  sides  there  was  a  further  loss  ranging  from  51  cents 
per  thousand  board  feet  in  lumber  taken  directly  from  the  kiln  to 
$2.27  per  thousand  board  feet  in  that  stored  in  the  sheds.  More 
checking  occurs  in  western  yellow  pine  when  the  kiln  is  crowded  or 
the  lumber  piled  close  together  than  when  there  is  ample  room  for 
circulation.  The  thicker  the  lumber  the  greater  is  the  deterioration 
due  to  check. 


320  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION 


DOUGLAS  FIR 

The  upper  grades  of  Douglas  fir  are  very  successfully  kiln-dried. 
Experience  has  shown  that  in  this  locality  it  does  not  pay  to  air-dry 
the  upper  grades  of  this  species  and  that  kiln-drying  is  the  only  prac- 
ticable method  of  getting  it  through  with  anything  like  its  original 
grade.  Approximately  91  per  cent  of  the  upper  grades  of  Douglas 
fir  one  inch  in  thickness  retained  the  original  grade  when  shipped  after 
being  kiln-dried.  The  average  loss  through  deterioration  due  to  kiln- 
drying  was  53  cents  per  thousand  board  feet  for  1-inch  lumber  and 
$2.90  per  thousand  board  feet  for  2-inch  lumber,  which  checks  very 
badly. 


REFERENCES 

"Oxidizing  Enzymes  and  Their  Relation  to  Sap  Stain  in  Lumber,"  I.  W. 
Bailey,  Botanical  Gazette,  Vol.  50,  pp.  142-147,  1910. 

"Bine  Stain  on  Lumber,"  Caroline  Rnmbold,  Science,  Vol.  34,  pp.  94-96, 
1911. 

"Principles  of  Drying  Lumber  at  Atmospheric  Pressure,"  H.  D.  Tiemann, 
Bulletin  104,  Forest  Service,  U.  S.  Dept.  of  Agr. 

"The  Prevention  of  Sap  Stain  in  Lumber,"  H.  W.  Weiss,  Circular  192, 
Forest  Service,  U.  S.  Dept.  of  Agr. 


